Tuning indicator tube



June 28, 1938.

H. M. WAGNER 2,122,269

TUNING INDICATOR TUBE Filed Sept. 29, 1937 INVEN TOR. 1 HERBERT M.WAGNER ATTORNEY.

Patented June 28, 1938 UNITED STATES PATENT OFFICE TUNING INDICATOR TUBEDelaware Application September 29, 1937, Serial No. 166,252

6Claims.

My invention relates to electron discharge devices, more particularly tosuch devices useful as visual indicators of voltage and having afluorescent electrode which is rendered luminous and has the appearanceof a pattern of light, which changes in response to the change in themagnitude of the applied voltage, a device of this char acter beingparticularly useful as a tuning indicator in radio receiving sets. Thepresent invention is a modification of the device of the characterdescribed and claimed in my Patent No. ,0 189 issued August 18, 1936.

It is an object of my invention to provide an electron discharge deviceof this general character which is particularly suitable for use as atuning indicator in a radio receiving set in which resonance isindicated by a brilliant luminous glow in the form of a ring on theanode, and in which departure from resonance may be indicated by adecrease or an increase in the width of the luminous ring pattern.

One embodiment of such a. device useful as a tuning indicator anddescribed in the patent above referred to comprises an envelope havingwithin it a straight thermionic equipotential cathode provided with twoseparate emitting sections, one of which is surrounded by amplifierelements which may comprise a control grid and anode, and the other ofwhich is surrounded by the tuning indicator elements of the tubeconsisting of a straight control electrode parallel to the cathode and adish-shaped anode coated on its inner surface with fluorescent material,the dish-shaped anode being concentric with and surrounding the cathodeand the control electrode. In operation electrons flow from the cathodeto the fluorescent anode with sufficient velocity to bombard thefluorescent anode and render it luminous. The control electrodeisconnected to the amplifier anode and the tube so connected into areceiving circuit that when the circuit is tuned to resonance with anincoming signal the luminous portion of the plate is of a predeterminedwidth, preferably the device is so connected that the luminous portionof the anode of the tuning indicator portion is of. maximum width, thedark portion of minimum width, when the circuit is tuned to resonance,and preferably the entire anode is made fluorescent and-th dark portiondisappears. According to the present invention, the indicator section ofthe tube is so designed that it forms a luminous annulus or ring oflight, the width of which varies with voltage variations. The tuningindicator-elements could of course be incorporated as a unit in anenvelope separate from the control grid and anode.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, but theinvention itself will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFigure 1 shows an electron discharge device embodying my invention withparts broken away to show details of construction; Figures 2 and 3 aretop views showing the tuning indicator portion of the tube and thepattern of light under different voltage conditions; Figure 4 is aperspective view of a modification of the electrode construction of thetuning indicator section of a tube made in accordance with my invention;Figure 5 is a section of another modification of the tuning indicatorportion of the device shown in Figure l; and Figure 6 is a circuitdiagram embodying a tuning indicator tube made in accordance with myinvention.

The electron discharge device or tuning indicator tube shown in Figure 1comprises an evacuated envelope l provided with the usual stem and pressII and base I2. Supported from the press are a cathode l3, preferablythe conventional indirectly heated equipotential type, and a grid I 4concentric and preferably coextensive with and surrounding the cathode,and an anode I surrounding the grid. While shown as a trlode thisportion of the tuning indicator tube could be of any other multi-elementtype.

In accordance with my invention the tuning indicator elements of thetube are placed at the upper end of the mount. The cathode I3 isextended upwardly and provided with a second emitting section [6adjacent which is placed the control electrode H which may be a collaror ring surrounding the cathode near the lower end of the emittingsection It. This control electrode I! is supported from and connected toone of the side rods i8 of the anode i 5. Surrounding and concentricwith the emitting portion l8 of the cathode is an anode or target whichmay be cupshaped and having only on its bottom 20 a coating 2|fluorescent under electron bombardment. The electrons emitted from thecathode and striking the anode with suflicient velocity cause it tofluoresce. The collar portion 22 of the anode it prevents electrons fromreaching the glass walls of the envelope.

In this type of tuning indicator the electrons travel radially outwardfrom the cathode to the fluorescent coating on the anode in a wide beam.

The extent of the fluorescent surface of the anode reached by theelectron beam is determined by the voltage on the control electrode ii.The less negative this electrode is with respect to the anode i9, thatis the more positive with respect to the cathode IS, the greater thearea of the anode covered by the beam and the greater the area of thefluorescent portion of the anode. According to my invention, the controlelectrode i1 is at a positive potential with respect to the cathode. Theadvantages of this are that the boundaries of the electron beam aresharp and well defined, there can be a high concentration of electronsat the edges of the luminous areas of the anode so that the edges arebrighter and stand out more prominently, a. high current to theluminescent anode and hence high luminosity is obtained with low anodevoltages, and the control electrode can be coupled directly to anamplifier. I have found also that a tube made in accordance with myinvention is not critical to variations in cathode temperature, and thatit can also be used with either alternating or direct voltages andcurrents.

The tube is viewed from the end so that the pattern of light is viewedas shown in Figures 2 and 3. As shown in Figure 2 and the dotted linesin the left hand side of Figure 1 when the control electrode is at apotential near that of the cathode most of the electrons go to theuncoated walls 22 and the anode fluoresces only over the small areashown as a thin ring indicated by the shaded lines in Figure 2. As thecontrol electrode ll becomes more positive the electron stream is pulleddown as shown on the right hand side of Figure 1 and more of thesurfaces of the anode fluoresces until at a predetermined voltage theentire suriace of the bottom 20 of the anode l9 fluoresces. This is thepattern which is shown in Figure 3 as a wide ring and which is obtainedwhen the circuit in which the tube is used is tuned to resonance. Therange of indication can be made all the way from maximum dark space withno ring of light to a maximum bright area comprising a wide ring oflight. i

In the modification shown in Figure 4 the anode lea is a cup-shapedmember having sloping sides coated on the interior with a fluores centcoating 2la, the upper edge being provided with a vertical wall or lip22a which is not coated. At the lower end of the coated portion of thecathode i6 and closely spaced from the bottom 20a of the cup-shapedmember i9a is the ring-like control electrode Ila. When the ring-likemember Fla is made sufllciently negative with respect to the fluorescentanode none of the electrons from the cathode reach the fluorescentcoating but substantially all go to the lip 22a. As the controlelectrode Fla is made more positive the electrons are pulled down towardthe control electrode so that a fluorescent ring appears on the coatedportion of the anode iBa it being of greatest width when resonance isattained. Resonance could also be indicated by having the entirefluorescent coating lighted at all times except when resonance isattained in which case the negative control electrode would be madeincreasingly negative as resonance is approached so that none of theelectrons are permitted to reach the fluorescent coating.

In Figure is shown a further modification of my invention. In this casethe cathode iSa is provided with a rounded end extending just above thebottom of the cup-shaped anode 20. The control electrode I! is similarto that shown in Figure 1. The anode I! however is closed at the top bymeans of a wire mesh screen 23 which may be welded to the wall or lip 22of the cupshaped member or insulatingly supported by the anode andconnected to some other electrode, for example, the cathode forobtaining diflerent control characteristics. The modification shown inFigure 5 operates in the same manner as that shown in Figures 1 and 2.

In Figure 6 I show a circuit embodying a tube ,made in accordance withmy invention. The

anode l5 of the triode section and the anode iii of the tuning indicatorsection are electrically connected to each other through a resistor 25.The fluorescent anode is connected directly to a source of voltagesupply 26. When no current flows from cathode i3 there is no voltagedrop in resistor 25 and the anode i5 and control electrode II, which isconnected to it, are at substantially the same potential as the anodeiii of the tuning indicator section of the tube. Under these conditionsthe pattern of light forms a wide ring as shown in Figure 3, and theanode fluoresces around its entire bottom surface. When a current flowsin the circuit of the anode ii a potential drop develops across theresistor 25 so that the anode i5 and control electrode II are made morenegative with respect to the anode or target of the tuning indicatorsection of the tube 20, and the control electrode approaches thepotential of the cathode, producing a thin ring pattern of light such asindicated in Figure 2, or no light at all. The magnitude of the currentthrough the triode portion of the tube is determined by the bias on thecontrol grid M.

In the circuit shown, a diode detector or rectifier 21 has its anode 28and its cathode 29 connected to opposite sides of the secondary of theintermediate or radio frequency transformer 32 tuned by condenser 36,the cathode being connected through the resistor 30 and by-passcondenser SL The cathode side of the transformer 32 is connected to thecontrol grid l4 through resistor 33, the grid being by-passed by meanso1 by-pass condenser 34 so that a bias is impressed on the grid H. Theconductor 35 may be connected to the automatic volume control circuit.In the arrangement shown with the set unturned and no signal passingthrough the transformer 32, no current passes through resistor 30 and nobias is developed. The grid i4 is at ground potential and permitscurrent to flow through the triode section of the tube under whichconditions the control electrode i1 is at a potential near that of thecathode as described above, the light pattern takes the form shown inFigure 2. With the set tuned to a signal a rectified current passesthrough resistor 30 developing a drop across this resistor andimpressing a bias on the control grid i l of the triode through theresistor 33. This reduces the current passing through the triode inproportion to the bias impressed upon the grid so that the controlelectrode i'i becomes more positive with respect to the cathode II. Theconstants of the various elements are so chosen that when tuned toresonance the pattern of light is of the greatest width and forms thepattern shown in Figure 3.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it

will be apparent that my invention is by no means limited to the exactforms illustrated or the use indicated, but that many variations may bemade in the particular structure used and the purpose for which it isemployed without departing from the scope of my invention as set forthin the appended claims.

What I claim as new is:

1. An electron discharge device having an envelope, a cathode withinsaid envelope for emitting electrons, a 'cup shaped anode surroundingsaid cathode and havingits interior surface coated with a fluorescentmaterial for receiving electrons from said cathode to produce a luminousannular shaped pattern on said anode, a control electrode comprising aring positioned between said anode and said cathode and surrounding thecathode for determining the area of the fluorescent surface of the anodereached by the electrons from said cathode.

2. An electron discharge device having an en velope, a cathode withinsaid envelope for emitting electrons, a cup-shaped anode surroundingsaid cathode and having its interior surface coated with a fluorescentmaterial for receiving electrons from said cathode to produce a ringlikepattern of light, a ring-like control electrode between said cathode andsaid anode and surrounding the cathode, said ring-like control electrodebeing positioned adjacent the bottom of said cup-shaped member tocontrol the electrons from said cathode to the coated surface of saidanode to vary the width of the ring-like pattern of light on the coatedsurface of the anode.

3. An electron discharge device having an envelope, a cathode withinsaid envelope and having a coated portion for emitting electrons, acupshaped anode surrounding the emitting portion of said cathode andhaving its interior surface coated with a fluorescent material forreceiving electrons from said cathode to produce a luminousannular-shaped pattern on the anode. a

ring-like control electrode between said .cathode and anode andsurrounding the cathode, said ring-like control electrode beingpositioned near one end of the emitting portion of the cathode andadjacent the bottom of said cup-shaped member to control the electronsfrom said cathode to the coated surface of said anode to vary the widthof the annular-shaped pattern light on the coated surface of the anode.

4. An electron discharge device having an envelope, a cathode withinsaid envelope for emitting electrons, a cup-shaped member having a flatbottom surrounding said cathode and having the interior surface of thebottom coated with a fluorescent material for receiving electrons fromsaid cathode to produce a luminous annularshaped pattern on the bottomof said anode, a ring-shaped control electrode positioned around saidcathode adjacent the bottom of said anode for determining the area ofthe surface of the anode reached by the electrons from said cathode.

5. An electron discharge device having an envelope, a straightthermionic cathode within said envelope for emitting electrons, acup-shaped anode having sloping sides surrounding said cathode andhaving the interior surface of the sloping sides coated with fluorescentmaterial for receiving electrons from said cathode to produce a ringlikepattern of light, a flat ring-like control electmde between said cathodeand anode and surrounding said cathode, said ring-like control electrodebeing positioned adjacent the bottom of said cup-shaped member tocontrol the electrons from said cathode to the coated surface of thesloping sides of said anode to vary the width of the ring-like patternof light on the coated surface of the anode.

6. An electron discharge device having an envelope, a cathode withinsaid envelope and having its end coated with electron emitting material,a cup-shaped anode having straight sides and a flat bottom surroundingsaid cathode, the inner surface of the bottom of the anode being coatedwith a fluorescent material Ior receiving electrons from said cathode toproduce a luminous annular shaped pattern of light on said anode, aring-like control electrode surrounding said cathode and positionedbetween said anode and said cathode adjacent the bottom of said anodefor determining the area of the fluorescent surface of the anode reachedby the electrons from the oathode, and a mesh like screen covering saidcupshaped anode and secured to the top 01 said cupshaped anode.

T M. WAGNER.

DISCLAIMER 2,122,269.Herbert M. Wagner, Newark, N. J. Toma Imncuroa Tmm.Patent dated June 28, 1938. Disclaimer filed August 13, 1940, by theassignee,

Radio Corporation of America.

H 13' enters this disclaimer of claims 1, 2, 3, and 5 of said LettersPatent.

[ final Gazette September 8, 1940.]

will be apparent that my invention is by no means limited to the exactforms illustrated or the use indicated, but that many variations may bemade in the particular structure used and the purpose for which it isemployed without departing from the scope of my invention as set forthin the appended claims.

What I claim as new is:

1. An electron discharge device having an envelope, a cathode withinsaid envelope for emitting electrons, a 'cup shaped anode surroundingsaid cathode and havingits interior surface coated with a fluorescentmaterial for receiving electrons from said cathode to produce a luminousannular shaped pattern on said anode, a control electrode comprising aring positioned between said anode and said cathode and surrounding thecathode for determining the area of the fluorescent surface of the anodereached by the electrons from said cathode.

2. An electron discharge device having an en velope, a cathode withinsaid envelope for emitting electrons, a cup-shaped anode surroundingsaid cathode and having its interior surface coated with a fluorescentmaterial for receiving electrons from said cathode to produce a ringlikepattern of light, a ring-like control electrode between said cathode andsaid anode and surrounding the cathode, said ring-like control electrodebeing positioned adjacent the bottom of said cup-shaped member tocontrol the electrons from said cathode to the coated surface of saidanode to vary the width of the ring-like pattern of light on the coatedsurface of the anode.

3. An electron discharge device having an envelope, a cathode withinsaid envelope and having a coated portion for emitting electrons, acupshaped anode surrounding the emitting portion of said cathode andhaving its interior surface coated with a fluorescent material forreceiving electrons from said cathode to produce a luminousannular-shaped pattern on the anode. a

ring-like control electrode between said .cathode and anode andsurrounding the cathode, said ring-like control electrode beingpositioned near one end of the emitting portion of the cathode andadjacent the bottom of said cup-shaped member to control the electronsfrom said cathode to the coated surface of said anode to vary the widthof the annular-shaped pattern light on the coated surface of the anode.

4. An electron discharge device having an envelope, a cathode withinsaid envelope for emitting electrons, a cup-shaped member having a flatbottom surrounding said cathode and having the interior surface of thebottom coated with a fluorescent material for receiving electrons fromsaid cathode to produce a luminous annularshaped pattern on the bottomof said anode, a ring-shaped control electrode positioned around saidcathode adjacent the bottom of said anode for determining the area ofthe surface of the anode reached by the electrons from said cathode.

5. An electron discharge device having an envelope, a straightthermionic cathode within said envelope for emitting electrons, acup-shaped anode having sloping sides surrounding said cathode andhaving the interior surface of the sloping sides coated with fluorescentmaterial for receiving electrons from said cathode to produce a ringlikepattern of light, a flat ring-like control electmde between said cathodeand anode and surrounding said cathode, said ring-like control electrodebeing positioned adjacent the bottom of said cup-shaped member tocontrol the electrons from said cathode to the coated surface of thesloping sides of said anode to vary the width of the ring-like patternof light on the coated surface of the anode.

6. An electron discharge device having an envelope, a cathode withinsaid envelope and having its end coated with electron emitting material,a cup-shaped anode having straight sides and a flat bottom surroundingsaid cathode, the inner surface of the bottom of the anode being coatedwith a fluorescent material Ior receiving electrons from said cathode toproduce a luminous annular shaped pattern of light on said anode, aring-like control electrode surrounding said cathode and positionedbetween said anode and said cathode adjacent the bottom of said anodefor determining the area of the fluorescent surface of the anode reachedby the electrons from the oathode, and a mesh like screen covering saidcupshaped anode and secured to the top 01 said cupshaped anode.

T M. WAGNER.

DISCLAIMER 2,122,269.Herbert M. Wagner, Newark, N. J. Toma Imncuroa Tmm.Patent dated June 28, 1938. Disclaimer filed August 13, 1940, by theassignee,

Radio Corporation of America.

H 13' enters this disclaimer of claims 1, 2, 3, and 5 of said LettersPatent.

[ final Gazette September 8, 1940.]

